Prognostic factors in hormone receptor positive oligometastatic breast cancer.
Authors: Lacaze Jean Louis, Bastien Cabarrou, Gauthier Glemarec, Clémence Brac de la Perrière, Thibaut Cassou Mounat, Ciprian Chira, Eleonora De Maio, Eva Jouve, Carole Massabeau, Vincent Nicolai, Mony Ung, Florence Dalenc
Journal: Journal of Clinical Oncology (2023)

1058 Background: Some recommend curative treatment for oligometastatic breast cancer (OMBC). To date, no randomized clinical trial has demonstrated the benefits of such a strategy. We present the largest retrospective series of patients treated consecutively for ER and/or PR positive (HR+) OMBC in a single institution. The objective was to describe the clinical and biological characteristics and prognostic factors of HR+ OMBC. Methods: We retrospectively reviewed all patients treated consecutively from 2014 to 2018 at our institution for synchronous or metachronous metastatic breast cancer (MBC). HR+ OMBC was defined as MBC with up to five metastases at diagnosis, positive hormone receptor status, and no other inclusion criteria. Clinical and biological characteristics, treatment modalities - intent-to-cure vs palliative - and outcomes were recorded. Progression-free survival (PFS) and overall survival (OS) were calculated. Log rank test and Cox regression models were used for survival analyses including time-dependent variable. Results: Of 998 patients treated for MBC within our institution between 2014 and 2018, 11.3% (N=113/998) met inclusion criteria. 62.5% of them had SBR grade I/II HR+ OMBC and 80.5% had HR+/HER2- OMBC. 89.3% patients had only one organ involved. None had more than two; 89.3% patients had 1-3 metastases at diagnosis. Among these 113 patients, 63.7% had bone metastases, 54.9% had bone only metastases, 19.5% had visceral metastases, 17.7% had lymph node metastases, 7.1% had brain metastases, and 3.5% had other metastases. Forty-one patients (36.3%) were treated in a curative intent with systemic treatment plus ablative focal treatment of primary tumor – or local relapse – and all distant metastases. Median follow up was 67.2 months (95%CI= [63.1-75.4]). For the entire series, five-year PFS and OS were respectively 35.2% (95%CI= [25.6-44.6]) and 67.0% (95%CI= [56.7-75.3]) respectively. In univariable analysis, liver metastases was associated with worse OS (HR=3.13, 95%CI=[1.43-6.87], p=0.003). In multivariable analysis, HER2 positive status (HR=0.43, 95%CI= [0.21-0.90], p=0.024), bone only metastases (HR=0.46, 95%CI= [0.27-0.78], p=0.004), and intent-to-cure treatment (HR=0.53, 95%CI= [0.30-0.93], p=0.027) were significantly associated with longer PFS. In multivariate analysis, only intent-to-cure strategy was associated with better OS (HR=0.24, 95%CI= [0.09-0.60], p=0.002). Conclusions: This is the largest retrospective series of patients treated consecutively for HR+ OMBC to date. 71.5 % of OMBC and 11.3 % of all MBC are HR+ OMBC. Most had only one invaded organ and 1-3 metastases. Among our cohort, intent-to-cure treatment improve drastically HR+ OMBC PFS and OS. A multimodal intent-to-cure strategy should be routinely discussed for patients with HR+ metastatic breast cancer with one to five metastases at diagnosis.